The following information is provided to assist the reader to understand the technologies disclosed below and the environment in which such technologies will typically be used. The terms used herein are not intended to be limited to any particular narrow interpretation unless clearly stated otherwise in this document. References set forth herein may facilitate understanding of the technologies or the background thereof The disclosure of all references cited herein are incorporated by reference.
A supplied-air respirator system such as self-contained breathing apparatus (SCBA) permits a person to breath in hazardous environments such as fires and confined spaces where breathing would be difficult or impossible without mechanical aid. A supplied-air respirator can, for example, include a full facepiece, a harness and carrier assembly, an air cylinder full of high pressure compressed air for breathing and at least one, and more typically two, air-pressure regulators. The first or first-stage regulator is typically mounted near the air cylinder and functions to reduce the relatively high pressure of the compressed air from the air cylinder to above atmospheric pressure. The air cylinder typically contains air or gas under high pressure (for example, 2200 psi to 4500 psi). The first stage regulator can, for example, reduce the pressure to about 80-100 psi. The second or second-stage regulator is typically mounted on the facepiece and functions to adjust the flow of air to meet the respiratory needs of the user. Respiration-controlled regulator assemblies are disclosed, for example, in U.S. Pat. Nos. 4,821,767 and 5,016,627 and U.S. Patent Application Publication No. 2012/016,0245.
The facepiece or face mask, which is sealed to the face of the user, typically includes a lens through which the user can view the surrounding environment. The facepiece also includes a port or mount for fluid connection with the second-stage regulator through which inspired air passes into the face mask and an exhalation port through which expired air passes out of the mask. The user's respiration controls a valve system (for example, including an inhalation valve and an exhalation valve) to control delivery of pressurized air via the second-stage regulator. Often, it is desirable to maintain a slight positive pressure within the facepiece relative to ambient pressure. Facepieces for supplied-air respirators in which a positive pressure is maintained within the facepiece are often referred to as pressure demand facepieces, while other facepieces for supplied-air respirators are often referred to as demand facepieces.
SCBAs typically utilize a hose to supply air from the first stage regulator to the facepiece through the second stage regulator. In some SCBAs, an electrical cable is used to provide electrical power to the facepiece. In a number of SCBA systems, the cable is routed to the facepiece along with the air hose. Movement of the SCBA on the user results in twisting, pulling, and significant straining of the cable. Such straining of the cable can result in damage to the cable, increasing the potential for malfunction or failure of the electronics on the facepiece. Moreover, the cable can be exposed to the external environment and presents a risk of snagging or catching on obstacles, which can damage the cable or create a condition for the user and the SCBA to become entangled.